APPLICATION
 
 

 

 

 


LEADING CERAMIC TILE FACTORY OVERCOMES WATER SHORTAGES BY TREATING AND RECYLING PROCESS WASTERWATER USING CHITOSAN 

 

EDWARD O. DINGILIAN, P.E.     T.S. Yau*    S.T.YAU** 

 

 

Supply and chemistry of the water are crucial factors to manufacture high quality ceramic tiles. The industry being an intensive user of water, tile manufacturing operations are often located close to river fronts where access to water is available year-round.

 

Select quality of rocks and clay earths are crushed in a rotary ball mill to specific mesh size. The crushed powder is sieved, dyes and water are added to form a slurred paste, which is pressed in moulds, then progressively dried, and glazed in drying tunnels. The tile surface is honed and polished using water jet rotary polishing wheels, then sized, inspected and packed. Tile polishing operation generates small mesh and submicron size pigmented particles that are gravity transported in the wastewater via the floor drains.

 

Suspended and dissolved solids in the supply water adversely affect true color of the dyes, tile strength, and the finished quality of the polished surface. Drought conditions adversely affect supply and chemistry of the river water, requiring pre-treatment to remove silt, organic matter, and pH adjustment. The production process of the factory requires to operate 24 hours a day, 7 days a week, and maintain steady supply of water.

 

To assure year-round supply, closely monitor chemistry of the water, and overcome production stoppages due to lack of river water, the MEI Ceramic Tile manufacturing factory installed a high rate, continuous flow automated treatment plant using state-of-the-art technology to recycle the process wastewater. United Chitotechnologies, Inc, IBS Corp., USA designed and supervised installation of the wastewater treatment plant.

 

The factory is located by the waterfront and draws its partial water needs from the river. River water chemistry is affected by environmental conditions, often with wide swings, depending on the length of the rainy season or drought, upstream water consumption, and unpredicted municipal discharges. The production water requirement is 3050 m3/day (0.81 mgpd), of which the major portion is used by the tile polishing stations, and the balance is non-recoverable steam from tile drying process.

 

Three options were evaluated to assure year-round availability and close control of the water chemistry to the factory:

. 100% city fresh water, treat the process wastewater to regulatory permit levels prior to

  discharging the effluent to the river.

. 100% river water, treat the influent, then treat the process wastewater to regulatory

   permit levels prior to discharging the effluent to the river.

. Draw partial water requirements from the river, add to process wastewater, then treat the

   water to the specified quality and recycle the treated water.

 

Typical analysis of the river water

 

Properties

Conc., mg/l

BOD

50.0-80.0

COD

100.0-200.0

Tot. hardness, as CaCO3

75.0-126.0

Calcium

42.0

Magnesium

5.0

Iron

3.0

Manganese

4.0

Chloride, as Cl-1

8.6

Sulfate, as SO4-2

30.0

Nitrate, as N

35.0

Bicarbonate, as CaCO3

275.0

TSS

100.0-250.0

Organic oils

15.0-30.0

                                     

Turbidity, NTU

60.0-850.0

pH

6.2-9.0

 

 

The river water is high in soluble calcium and magnesium in bicarbonate form. The unusually high levels of iron and manganese discolor the tile if the iron and manganese are not removed prior to adding to the tile clay paste. The river water analysis also revealed  presence of organic matter, including amino acids characteristic of raw

human/ animal untreated waste discharge to the river.

 

Bench scale tests conducted on process wastewater collected from side streams during various hours of the day over a one week period established the optimum application dosages of the polyelectrolyte and equipment design parameters. Since organic load is absent in the process wastewater, physical-chemical treatment was selected.

 

Benefit to cost evaluation showed the natural cationic polymer chitosan of specific molecular weight range and deacetylation in conjunction with another electrolyte to be the appropriate choice, because of the high particle sedimentation velocity, leading to shorter retention time, comparatively smaller treatment equipment and floor space. Chitosan application also removed 70%-85% of the soluble iron and manganese. The solution was effective in removing hydrocarbons and organic oils. Most importantly the settled solids could be safely land applied because chitosan is biodegradable..

 

The cost effective and environmentally friendly choice technology was to partially draw the  river water, add to the process wastewater, treat the combined wastewater and then recycle the treated water. Cost of the treatment at the application dosages was the economical option, and assured continuous availability of water to the factory.

 

Process wastewater collected from the floor drains is pumped to the treatment plant surge equalization tank. River water is introduced to the same tank to top-off the volume and compensate water lost as steam during the tile drying process. The wastewater is automatically pumped from the equalization tank to the flash mixing tank where chitosan and electrolyte solutions are injected. The water then passes to the settling tank where the flocculated solids gravity sediment. The sedimented solids are periodically pumped to a solids thickening tank, and the treated water is automatically pumped to a 200m3 storage tank that corresponds roughly to 3 hours of plant needs.

 

Equipment bill of material:

. Surge equalization tank with transfer pumps

. Polymers preparation tanks, mixers, transfer pumps

. Polymers usage tanks, metering pumps

. Flash mixing tank with mixer

. Settling tank with solids transfer pump

. Effluent flow equalization tank with transfer pump to storage tank

. Electrical panel, disconnects, automatic flow controls, interlock relays

 

The 3050 m3/day wastewater treatment plant floor space is 400 m2 with 8 meter clear ceiling height. The wastewater treatment electrical power averages 35 Kwh. The installation meets and exceeds consistently the water quality requirements of the plant.

 

Schematic flow diagram of the process wastewater treatment

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


CERAMIC  TILE 04/02

 

________________________________________________________________________

Edward O. Dingilian, P.E. President, United Chitotechnologies, Inc., IBS Corp. USA

(*)   T.S. Yau, Director  & General Manager Mei Ceramic Tile Co.,

(**) S.T. Yau, Exec. Vice President, United Chitotechnologies, Inc. USA, Aquaspan, USA

Correspondence to: Edward O. Dingilian, P.E.,  (e-mail: Edingilian@aol.com)

 

April 2002